This shared equipment proposal brings together a diverse group of twelve investigators from multiple Departments at Northwestern University Medical School. The group works on a wide range of organisms that include viruses (Longnecker), bacteria (Seifert) protozoa (Engman and Haldar) and mammalian cells (Borisy. Green, Reddy, Miller). Their studies encompass diverse cellular processes that range from antigen processing, T cell activation, cell migration, junction formation, cell division, adhesion and invasion of pathogens and novel eukaryotic organdlies. The focus of the group is to first examine protein expression, organization and transport in both living and fixed cells/tissues and then correlate protein expression and distributions with cellular events of transport and signaling, as regulated by prokaryotes, lower eukaryotes and mammalian cells. The applications described are in Host-pathogen interactions, Mammalian Cell Biology, Motility, Immunology. The DeltaVision microscope will enable investigators to have : 1) simultaneous acquisition of triple-labeled specimens; 2) higher optical efficiency for light collection system for low intensity specimens; 3) increased resolution (150 nm vs. 200 nm for confocal) for studying details of cell structure; 4) DIC; and 5) visualization of nuclei with UV dyes. This microscope fulfills all of the different experimental requirements of the group. For all eight investigators, experiments with a "leased? DeltaVision microscope or access to a similar microscope at other universities, have resulted in important new cellular insights. The microscope will be centrally located in an existing Imaging Facility that has well established training and technical support programs, and is used over 70 PIs (and an even larger number of affiliated Research Faculty, Postdoctoral Fellows, Graduate Students and Research Associates) from 20 basic science and clinical departments in the Medical School. A DeitaVision microscope on lease has been used by 44 users indicating its demand. The purchase of the DeitaVision microscope will provide a ?state-of-the-art? microscope that can be applied to studying a wide range of applications. It will also enhance scientific interactions between investigators working in diverse areas of biology and human health in the school.